Thomas County cat. [volume] (Colby, Kan.) 1885-1891, 1887-06-02
IRON cRYsrALllzATIoN.



How 1t Produces Changes I. the Fzh.e, .
the Metals and weakens 1t.
Since passenger train on the Nortl
British railway plunged from the grea
bridge over the Firth of Tay into tn,
dark waters below. one stormy Deccm
Der night seven years ago. carrying ev
er; living soul upon it to certain death
there has been no railroad bridge dis
aSter that has excited so much publ.
attention as that which occurred on the
Boston & Providence railroad at tn,
BusSey bridge near Boston. In both tn,
cause appears to have been structural
defect This may also be said of tn,
Ashtabu.a accident. whose horrors, how
ever, were increased by the fierce wors
of flames and the inclemencies of bit.
.erly cold winter night.
Bridge accidents are considered by
all railroad men as incomparably the
worst to which travel BY rail is exposed,
and as among the most difficult to
guard against absolutely. One source
of danger was shown when the peculiar
effects Of a locomotives hammer blows
upon track were explained. The
theory was advanced that a girder OF
the bridge had broken beneath the en-
gine's drivers, whose pounding upon
the effectively constructed bridge was
thus primarily the cause of the acct
dent. This brings up phase of rail
road and bridge accidents which is at
present receiving a great deal of atten-
ton. Capitalization in the material of
iron bridges is an element of danger
now so we'll recognized that the Penn
sylvania Railroad Company has adopted
the definite policy of substituting stone
for iron bridges, and the same plan is
being followed by other railroad COM
panies.
The lifetime of an iron bridge is from
twenty to twenty-five years. and con-
slant care is necessary to insure its
safety. The Ashtabula bridge was
thirteen years old. and at the time it
fell beneath the weight of two engines
and q heavy express train the theory
was commonly advanced that crystal
ization had impaired its original
strength. The two great moving causes
Of crystallization are vibration and the
hammer blows of the locomotive, which
gradually, by repeated impact, turn the
fiber of iron or steel into a mass of
needing only some unusual
pressure or blow TO cause them to
break apart. Add to this the oscillation
caused by the passage of trains at
high rate of speed, and it will be seen
that an iron bridge is exposed to pecu-
liar perils, which can only be guarded
against by rigid inspection and con-
slant renewals.
Capitalization was one of several
theories advanced by Park Benjamin.
New York engineer, to account for the
Tay bridge accident He said:
General indications 60 to show that
the cause must be sought in an abnormal
condition Of the structure. or rather one
which did not enter into the calculations
Of the builders. Such condition would
be the deterioration Of the metal BY its
change from fibrous to a crystalline
state under repeated vibration. That
his occurs in railway bridges has been
disputed by many we'll
Known engineers. On the other hand.
many examples are quoted by different
authorities to support the theory. APP
,ropos to this particular accident.
French engineer and iron
ounder now in this country informs us
hat he has known bars of iron made by
himself from Scotch pig to change from
| tough fibrous to brittle crystalline
in travelling by rail only from
he north of France to Paris. This is, of
course. an extreme instance.
Again. recent research has DEM
that because structure
large quiescent load that
act is little proof of stability under re-
,eated shocks and vibrations. Metals
re believed to have life A bar. for
may stand million vibra-
ions and break down at the million
md first. and yet the last shock may be
lighter than preceding ones. Attempts.
.owever, to reduce this law to
PRACTICAL application have elected
n abundance of conflicting evidence;
ut, nevertheless. it is well settled that |
n no department Of mechanics is an
xtendcd course Of actual experiment.
ne more urgently needed or of graver
ublic importance.
The strength of the Tay bridge at the
ime of its building was such that it
Tas pronounced perhaps the most
structure in the world"
British magazine, speak
~ of its test, when FIVE engines, |
-eiShing $50 tons, were placed on a
ingle span. said: 1.-The result is the
omplete establishment of this fact $50